One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic tvb now,tvbnow,bttvb) R! I% V3 ]; O- } j
eruptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are tvb now,tvbnow,bttvb9 b0 j$ ?2 F% Q$ V9 M
active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.5 f2 i: N' D0 H* Y. K2 y
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens, ) n q+ b$ @2 p- H. r+ f
erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
3 I, ~: ?2 B% j8 S6 V5.39.217.77and explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. tvb now,tvbnow,bttvb) j2 e7 ?9 i: S+ K" b
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape.
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above TVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。5 _' b3 `- {/ b+ E6 j1 w0 t
of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewasTVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。5 J9 S. O2 v! \
taken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash
3 ^6 t4 x e2 ^( m0 S2 u5 w; G: wTVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。plume reached as high as 50,000 feet.
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6 [) n3 `" q! ~1 ^1 e7 f3 EAugustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra 公仔箱論壇' {" i( D8 n! x3 c1 {8 G) B2 M2 @1 S1 p' @
satellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 : T0 A7 r6 u3 a. B ^7 r+ N9 o
years. The island’s jagged edges were created by massive avalanches.
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0 J$ Q) T& |# Y5 A9 g6 ?5.39.217.77Augustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring 5.39.217.77! X; C+ }/ z" |- m
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet tvb now,tvbnow,bttvb: v. E7 n. l% N) R
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of
( p0 I$ e6 R; N5.39.217.77the continental crust, creating magma that drives the volcanic eruptions
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( L: d- c/ I8 Q Ctvb now,tvbnow,bttvbAstronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano
$ h \/ t/ B5 F5.39.217.77in the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.
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The smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising B2 m9 z1 U, p1 a; V& w3 y7 [
and cooling of the air above. In contrast, a dark gray cloud of ash near the ground is probably an avalanche of hot ash and rock known
5 e# N: p2 L- A7 F$ ^* p公仔箱論壇as a pyroclastic flow.TVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。1 @) E# G a. X; o. M' |; S. J; v
* M4 s z3 m! z6 N& x/ X% k; c5 \9 Ltvb now,tvbnow,bttvbThis photo sparked a debate among scientists about what caused the hole in the clouds above the eruption. Three possible options came up:
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* It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.& B0 L5 ?+ H2 ^) j" W0 z
* A shockwave from the eruption could have blown a hole in the cloud deck.
3 i1 z0 b" D- r1 @% x * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.
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TVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。) g0 s' @$ I( K( E* e
Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet.
7 C: s( L( ~3 I/ ?* J1 ^tvb now,tvbnow,bttvbIt continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
5 T9 W( P, h- [. | N4 ? the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.TVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。3 o9 p* g0 j8 o* \( J0 q! o, X
7 C5 c! X2 K. KTVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。Redoubt is a 10,200-foot tall stratovolcano 100 miles southwest of Anchorage in the Aleutian Range, west of the Cook Inlet.
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' p- S5 O3 b. Y# Z公仔箱論壇Mount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in
" ^8 o/ [6 ^6 n2 g' [ the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one 公仔箱論壇5 U1 p( j/ \7 k
captured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in tvb now,tvbnow,bttvb' w3 T: ?% Q- h
this picture are from forest fires ignited by lava.
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/ A. w+ o: Z! E6 I6 o5.39.217.77Etna is a stratovolcano located on the island of Sicily. It is one of the most studied volcanoes in the world and. at 500,000 years old, it may公仔箱論壇4 B8 V/ @3 |" Z1 I; R+ y
also be the oldest-known active volcano.
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A NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high
: M; n u T2 b& e7 r; Gand claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.
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Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City.
" G# {* n0 D3 Q0 B" E; l" i! n5.39.217.77The second highest peak in Mexico at 17,800 feet, this glacier-covered stratovolcano has erupted at least 20 times in the last 500 years and has caused
; m5 l9 l7 t% P5 \9 P, Lmultiple evacuations of the city. This eruption in 2001 was caught by astronauts on the International Space Station, near the end of a seven-year period / P- T2 \8 K1 Y! _( r# b" ?
of frequent activity. The plume reached heights of around 30,000 feet.
$ L& H M$ i' ]8 U5 v1 b5.39.217.77" e( o" X! Y' D- Q) W$ F
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0 R- s4 ]" |; a0 Q. atvb now,tvbnow,bttvb 5.39.217.77- d/ J$ f( H/ ?$ q8 _* n$ {5 x- [
6 s7 X3 |( c' g' h0 Z+ M* f9 PTVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the tvb now,tvbnow,bttvb5 m$ ?/ Q) H) l' q$ q4 h8 {+ N
west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.公仔箱論壇' t0 n% e& m9 U
1 M) K8 B# I" V; m公仔箱論壇Chaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic
2 N7 ]; Q% w1 r7 U6 E公仔箱論壇flows and volcanic mudflows called lahars. The caldera is relatively small at less than two miles wide, and sits on the flank of the larger Michinmahuida volcano.5 y5 Y4 @( l+ R d& i) O' @! ] K1 e
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This image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra
2 W$ t' x8 m3 Y' B8 J0 kTVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。is a shield volcano, which are made mostly of previous lava flows and tend to be broad and gently sloping. The Galapagos are part of an island chain
4 B2 y$ T+ s6 h' k5 s' Htvb now,tvbnow,bttvbformed by a hot spot where a plume of hot mantle rises up and melts the base of the ocean crust. As the Pacific plate moves over the relatively
' z3 m+ {* K( ~ P. pstationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.tvb now,tvbnow,bttvb3 F" u/ g+ ?9 _' f, o: J" V
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NASA’s Terra satellite snapped this image of Shiveluch volcano erupting on Russia’s Kamchatka peninsula at the edge of the Pacific Ring of Fire in 2004.
$ p# H; t+ T& o; S Y- VA lava dome had been growing in the volcano’s crater, followed by intermittent eruptions that lasted weeks. Shiveluch is a 10,400-foot-high stratovolcano
+ D7 o& \* R3 S6 R; Ztvb now,tvbnow,bttvbthat is at least 60,000 years old and has been erupting fairly often for the past 10 years. Its dome has collapsed multiple times, most recently in 1964,
& S0 m1 U4 t9 X' c* J8 C! tTVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。causing avalanches of debris into the crater. |